Blue luminescent complexes based on 5-aminodiacetic isophthalic ligand

Article abstract of DOI:10.1016/j.molstruc.2005.12.023

The reactions of Cd(CH₃COO)₂·2H₂O or Zn(CH₃COO)₂·2H₂O and 5-aminodiacetic isophthalic acid (H₄adip) with 1,10′-phenanthroline (phen) ligand gave rise to two blue luminescent coordination mononuclear complexes: [Cd(phen)(H₃adip)₂(H₂O)₂]·0.5H₂O (1) and Zn(phen)(H₃adip)₂ (2), respectively. 1 crystallizes in the triclinic space group P-1, with a=6.2889(2), b=16.1556(5), c=18.4277(7) A?, α=97.722(12), β=94.338(9), γ=95.039(7)°, V=1840.86(11) A?³, Z=2. Complex 2 crystallizes in monoclinic, space group C2/c with a=22.639(8), b=9.813(3), c=15.708(6) A?, β=110.928(4)°, V=3259(2) A?³, Z=4. Carboxylic groups in both structures are involved in strong hydrogen bonding interactions. At room temperature, complex 1 exhibits an intense emission at 474 nm upon 380 nm excitation, while complex 2 exhibits an intense emission at 485 nm upon 365 nm excitation, which are contributed from ligand-to-metal charge-transfer (LMCT).

Full text of DOI:10.1016/j.molstruc.2005.12.023

Journal of Molecular Structure 789 (2006) 220–224
www.elsevier.com/locate/molstruc
Blue luminescent complexes based on 5-aminodiacetic isophthalic ligand
*
Yanqing Xu, Baiquan Chen, Yaqiong Gong, Daqiang Yuan, Feilong Jiang, Maochun Hong
State key Laboratory of Structural Chemistry, Fujian Institute of the Research on the Structure of Matter, Chinese Academy of Sciences,
Fuzhou, Fujian 350002, People’s Republic of China
Received 17 November 2005; received in revised form 25 December 2005; accepted 27 December 2005
Available online 28 February 2006
Abstract
The reactions of Cd(CH3COO)2$2H2O or Zn(CH3COO)2$2H2O and 5-aminodiacetic isophthalic acid (H4adip) with 1,100-phenanthroline
(phen) ligand gave rise to two blue luminescent coordination mononuclear complexes: [Cd(phen)(H3adip)2(H2O)2]$0.5H2O (1) and
˚
Zn(phen)(H3adip)2 (2), respectively. 1 crystallizes in the triclinic space group P-1, with aZ6.2889(2), bZ16.1556(5), cZ18.4277(7) A,
3
˚
aZ97.722(12), bZ94.338(9), gZ95.039(7)8, VZ1840.86(11) A , ZZ2. Complex 2 crystallizes in monoclinic, space group C2/c with
3
˚
˚
aZ22.639(8), bZ9.813(3), cZ15.708(6) A, bZ110.928(4)8, VZ3259(2) A , ZZ4. Carboxylic groups in both structures are involved in strong
hydrogen bonding interactions. At room temperature, complex 1 exhibits an intense emission at 474 nm upon 380 nm excitation, while complex 2
exhibits an intense emission at 485 nm upon 365 nm excitation, which are contributed from ligand-to-metal charge-transfer (LMCT).
q 2006 Elsevier B.V. All rights reserved.
Keywords: Mononuclear; Supramolecule; Carboxylate; Hydrogen bond; Luminescence
1. Introduction
like other multi-carboxylate ligands, it can act not only as
hydrogen-bond acceptor but also as hydrogen-bond donor,
depending upon the number of deprotonated carboxyl groups,
which contribute to the stability of supramolecular network.
Recently, we began to assemble H4adip and transition metal ions
into polymeric complexes under hydrothermal conditions. We
hope the rich information stored in H4adip will induce novel
polymeric structures. Through carefully controlling the reaction
conditions, we have found that H4adip is a versatile building
block for the construction of metal-organic complexes through
complete or partial deprotonation of its carboxyl groups. A series
of interesting structures from 1D to 3D architectures have been
successfully obtained in our experiments [15]. Herein, we
reported two transition metal complexes derived from H4adip
and phen under strong acidic conditions: [Cd(phen)(H3adip)2
(H2O)2]$0.5H2O (1) and Zn(phen)(H3adip)2 (2). Such discrete
moleculesarefurther linkedtogether byhydrogenbonds orp/p
interactions to generate interesting supramolecular architectures,
and both show intense blue luminescence in solid state at room
temperature.
In recent years, chemists have devoted a great deal of effort to
metal-organic coordination polymers [1–5]. In particular,
aromatic multi-carboxylate ligands have been shown to be
good building blocks in the design of metal-organic materials
with desired topologies owing to their rich coordination
modes [6–9]. However, most adopted ligands possesses rigid
carboxylate arms, e.g. 1,3,5-benzenetricarboxylate [10], 1,2,4,5-
benzenetetracarboxylate [11], 1,4,5,8-naphthalenetetracarboxy-
late [12], etc. Relative fewer compounds are reported derive from
flexible carboxylate arms [13,14]. But as known that the crystal
structure formation is sensitive to the flexibility of carboxylate
arms, and such flexibility may increase the probability of making
tube-likeorcage-likestructure. Takingaccountofthese, wefeelit
significant to take on the exploration on carboxylate ligand with
flexiblecarboxylate arms. So, we designed and synthesized a new
bridging chelating multi-carboxylate ligand 5-aminodiacetic
isophthalic acid (H4adip). H4adip not only has two rigid carboxyl
groups, but also has two flexible acetic groups with suitable
lengths. Moreover, the nitrogen atom of aminodiacetic group is
alsopossibletoparticipate in the coordinationsphere. In addition,
2. Experimental section
2.1. General
*
Corresponding author. Tel.: C86 591 83792460; fax: C86 591 83714946.
E-mail address: hmc@ms.fjirsm.ac.cn (M. Hong).
The H4adip were prepared as described in our work
elsewhere [15], and the other starting materials were purchased
commercially and used without further purification. Elemental
0022-2860/$ - see front matter q 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2005.12.023

Y. Xu et al. / Journal of Molecular Structure 789 (2006) 220–224
221
Table 2
˚
Selected bond lengths (A) and bond angles (8) of complexes 1 and 2
analyses were determined on an Elemental Vario ELIII
elemental analyzer. IR spectra were measured as KBr pellets
on a Nicolet Magna 750 FT IR spectrometer in the range of 200–
4000 cmK1. Fluorescent spectra were measured on an
Edinburgh Instruments analyzer model FL920.
Bond
˚
length (A)
Bond angle
(8)
Complex 1
Cd(1)–O(18)
Cd(1)–O(8)
Cd(1)–N(2)
Cd(1)–O(14)
Cd(1)–N(1)
Cd(1)–O(17)
O(13)–C(36)
O(14)–C(36)
O(7)–C(13)
O(8)–C(13)
2.274(3)
2.306(3)
2.336(3)
2.340(3)
2.403(3)
2.412(3)
1.247(5)
1.278(5)
1.272(6)
1.235(5)
N(2)–Cd(1)–N(1)
O(8)–Cd(1)–O(14)
O(18)–Cd(1)–O(17)
O(8)–Cd(1)–N(1)
O(18)–Cd(1)–N(2)
O(18)–Cd(1)–N(1)
O(14)–Cd(1)–N(1)
N(1)–Cd(1)–O(17)
70.67(11)
152.75(11)
89.80(13)
87.36(11)
162.06(11)
113.45(12)
118.94(10)
152.48(12)
2.2. Synthesis of [Cd(phen)(H3L)2(H2O)2]$0.5H2O (1)
A mixture of Cd(CH3COO)2$2H2O (0.134 g, 0.5 mmol),
H4adip (0.148 g, 0.5 mmol) and 1,10-phen (0.099 g, 1.0 mmol)
dissolved in distilled water (6 ml)/CH3COOH (6 ml) was
sealed in a 25 ml Teflon-lined autoclave and heated under
autogenous pressure at 90 8C for 3 days. The resulting colorless
prismatic crystals of 1 were filtered, and air-dried at room
temperature. Yielded (0.157 g), produced in 67.6% (based on
H4adip). IR (KBr pellet, cmK1): 3425(br), 2972(w), 2911(w),
2844(w), 1696(s), 1602(s), 1468(s), 1423(s), 1383(m), 1325(s),
Complex 2
Zn(1)–N(2A)#1
Zn(1)–N(2)
2.0641(17)
2.0641(17)
2.1252(16)
2.1252(16)
2.2347(15)
2.2347(15)
2.517(2)
N(2A)#1–Zn(1)–N(2)
O(1)–Zn(1)–O(2)
81.92(9)
59.97(6)
153.73(8)
153.19(6)
105.37(6)
101.43(6)
96.43(6)
Zn(1)–O(1A)#1
Zn(1)–O(1)
O(1A)#1–Zn(1)–O(1)
N(2A)#1–Zn(1)–O(2A)#1
N(2)–Zn(1)–O(1A)#1
O(1)–Zn(1)–O(2A)#1
N(2)–Zn(1)–O(2A)#1
1383(m), 1293(m), 995(m). Anal. Calcd for C36H33CdN4O18.5
C 46.49, H 3.58, N 6.02%. Found: C 46.42, H 3.71, N 5.98%.
:
Zn(1)–O(2A)#1
Zn(1)–O(2)
Zn(1)–C(8A)#1
O(1)–C(8)
1.257(2)
2.3. Synthesis of Zn(phen)(H3L)2 (2)
O(2)–C(8)
1.262(3)
Symmetry code: #1 Kx,y,KzC1/2.
Complex 2 was synthesized by the same procedure as above
but adding Zn(CH3COO)2$2H2O instead of Cd(CH3COO)2$2
H2O. Pale-yellow prism crystals are obtained by filtration.
Yielded (0.075 g), produced in 36.2% (based on H4adip). IR
(KBr pellet, cmK1): 3436.9(br), 3075.6(w), 2921.54(w),
2865.02(w), 2361.7(w), 1718.63(vs), 1597.8(m), 1555.49(m),
1467.63(m), 1421.97(m), 1383.83(m), 1267.9(w), 1216.5(m),
1192.47(m), 990.58(m), 846.79(w). Anal. Calcd for
C36H28N4O16Zn: C 51.60, H 3.37, N 6.69%. Found: C 51.52,
H 3.42, N 6.64%.
2.3.1. X-ray structure analyses
X-ray intensity data of both complexes were collected on a
Mercury CCD diffractometer equipped with graphite mono-
˚
chromated Mo Ka radiation (lZ0.71073 A) at 173 K. Empirical
absorption corrections were applied to the data using the
SADABS program [16]. The structures were solved by the direct
method and refined by the full-matrix least squares on F2 using
the SHELXTL-97program[17]. Allofthenon-hydrogenatomswere
refined anisotropically. The H atoms bonded to C atoms were
positioned geometrically and refined using a riding model [C–H
Table 1
Crystallographic data for the complexes 1 and 2
˚
0.93 A and Uiso(H)Z1.2 Ueq(C)]. The H atoms bonded to O
1
2
atoms were located from difference maps and refined isotropi-
cally. Crystallographic data and structure refinements for 1 and 2
are summarized in Table 1. Selected bond lengths and bond
angles are listed in Table 2. CCDC numbers are 290056 for
compound 1 and 290057 for compound 2, respectively.
Empirical formula
Temp. (K)
C36H33CdN4O18.5
173(2)
C36H28N4O16Zn
173(2)
Cryst. color
Cryst. size (mm3)
Mr
Colorless
0.20!0.10!0.08
930.06
Colorless
0.20!0.10!0.05
837.99
Crystal system
Space group
Triclinic
Monoclinic
C2/c
PK1
˚
a (A)
˚
b (A)
˚
c (A)
6.2889(2)
16.1556(5)
18.4277(7)
97.722(12)
94.338(9)
95.039(7)
1840.86(11)
2
22.639(8)
9.813(3)
15.708(6)
90
a (8)
b (8)
g (8)
110.928(4)
90
3
˚
V (A )
3259(2)
Z
4
Density (mg/m3)
Abs. coeff. (mmK1
F(000)
1.678
1.708
)
0.684
0.846
946
1712
Refln collections
Indep. Reflns
Params
S on F2
14204
12279
8293 [R(int)Z0.0259]
547
3719 [R(int)Z0.0315]
314
1.142
1.076
R1, wR2 [IO2s(I)]
R1, wR2 (all data)
0.0534, 0.1176
0.0609, 0.1216
0.0393, 0.0928
0.0459, 0.0973
Fig. 1. ORTEP drawing of 1, drawn with displacement ellipsoids at the 30%
probability.

222
Y. Xu et al. / Journal of Molecular Structure 789 (2006) 220–224
Table 3
˚
Parameters (A, 8) for hydrogen-bonding interaction of complexes 1 and 2
in a trans arrangement, together with two oxygen atoms from
coordinated water molecules. The bond lengths of Cd–O in 1
˚
vary from 2.274(3) to 2.412(3) A and bond lengths of Cd(1)–
˚
N(1)/Cd(1)–N(2) are 2.336(3)/2.403(3) A, which are compar-
D–H/A
d(D–H)
˚
(A)
d(H/A)
˚
(A)
d(D/A)
˚
(A)
:DHA
(8)
able to those in reported Cd compounds [18–20]. However, the
˚
Complex 1
O(5)–H(5)/O(7)
0.84
0.84
0.85
0.84
0.84
0.84
0.84
0.85
0.85
0.85
1.69
1.73
2.63
1.75
1.74
1.78
1.73
2.14
1.97
2.09
2.489(5)
2.524(4)
3.431(5)
2.592(4)
2.574(4)
2.603(4)
2.567(4)
2.838(5)
2.745(4)
2.811(7)
158.6
158.1
157.3
174.7
170.2
165.9
175.6
139.6
151.2
142.7
Cd1/O13 distance of 2.774 A suggests a non-negligible
O(16)–H(16A)/O(14)
O(17)–H(17A)/O(16)
O(2)–H(2)/O(11F)#1
O(4)–H(4A)/O(3A)#2
O(10)–H(10)/O(9B)#3
O(12)–H(12)/O(1G)#4
O(18)–H(18A)/O(6D)#6
O(18)–H(18B)/O(15E)#7
O(19)–H(19A)/O(5C)#8
interaction between them, as may be described as a semi-
chelating coordination mode. Thus, one of H3LK ligand adopts
a bis-monodentate chelating coordinate mode, the other adopts
monodentate mode. Hence, the CdII center may be also
regarded as in distorted pentagonal bipyramidal geometry. The
face-to-face distances between phenyl ring of H3adipK and
0
˚
1,10 -phen ligand are 3.632 and 3.680 A, indicating the
existence of p/p stacking interactions.
Complex 2
Different kinds of hydrogen bonds are observed in the
complex 1 in Table 3: (i) hydrogen bonds between two
uncoordinated carboxylate oxygen atoms with an O/O
distance of 2.489(5)–2.603(4) A; (ii) hydrogen bonds of
uncoordinated water molecules/carboxylate oxygen atoms
O(6)–H(6A)/O(1B)#2
O(8)–H(8A)/O(4C)#3
O(3)–H(1)/O(2)
0.97(4)
0.90(3)
0.95(4)
1.77(4)
1.82(4)
1.63(4)
2.721(2)
2.667(2)
2.581(2)
164(3)
158(3)
177(3)
˚
Symmetry transformations used to generate equivalent atoms: for complex 1: #1
xC2, yC1, z; #2 KxC1, KyC2, KzC1; #3 KxC1, KyC1, KzC1; #4 xK2,
yK1, z. #5 xK1, y,z; #6 KxC1, KyC2, Kz; #7 Kx, KyC1, Kz; #8 KxC2,
KyC2, Kz. for complex 2: #2 Kx, Ky, Kz; #3 KxC1/2, KyK1/2, KzC1.
˚
(O/O distance: 2.811(7) A); (iii) hydrogen bonds of coordi-
nated water molecules/carboxylate oxygen atoms (O/O
˚
distances: 2.745(4)–2.838(5) A). As shown in Fig. 2a, the
3. Results and discussion
mononuclear units are linked together into a zigzag chain by
i
˚
hydrogen bonds of O4/O3A (2.574(4) A; A: KxC1, KyC
˚
Single-crystal X-ray diffraction analysis reveals that 1 is a
mononuclear complex. As shown in Fig. 1, the CdII center is
ligated by two nitrogen atoms from 1,100-phen, two
carboxylate oxygen atoms from two different H3LK ligands
2, KzC1); O10/O9B, (2.603(4) A; B: KxC1, KyC1,
KzC1). Meanwhile, the hydrogen bondsi of O5/O7 2.489(5)
ii
˚
and O16/O14 2.524(4) A, together with hydrogen bonds of
˚
O5/O19C (2.811(7) A; C: 2Kx, 2Ky, Kz), further
Fig. 2. (a) View of 1D chain formed by H3adipK extending along b-axis; (b) The coordinated water oxygen atom forms bifurcated hydrogen bondsii to link zigzag
chain along c-axis.

Y. Xu et al. / Journal of Molecular Structure 789 (2006) 220–224
223
bifurcated hydrogen bondsiii connectivity. The 2D layers are
i
˚
linked by hydrogen bonds of O2/O11F (2.592(4) A; F: 2Cx,
˚
1Cy, z) and O12/O1G (2.567(4) A; G: xK2, yK1, z) to give
rise to 3D architecture, as is shown in Fig. S1.
Single crystal X-ray analyses show that complex 2 also
features a mononuclear structure, which is composed of ZnII
center, one phen and two H3LK. ZnII is six-coordinated by two
nitrogen atoms from one phen and four oxygen atoms from two
H3LK ligands, as is shown in Fig. 3. The bond lengths of Zn–O
˚
in 1 vary from 2.1252(16) to 2.2347(15) A and bond lengths of
˚
Zn(1)–N(1)/Zn(1)–N(2) are 2.0641(17) A, which are compar-
able to those in reported Zn compounds [21–23]. But the two
H3LK ligands arrange in a cis way and deviate from phen rings.
As a result, no p/p interactions exist in such an isolated
molecule. Moreover, for the lack of the water molecules, only
hydrogen bondsi mentioned above was found in this structure.
˚
As shown in Fig. 4a, O1/O6B (2.721(2) A; B: Kx, Ky, Kz)
functions as linkage to link the mononuclear into a zigzag chain
along oc direction. The intramolecular hydrogen bonds O2/
˚
O3 with the distance of 2.581(2) A consolidate the framework.
The perspective of the chain viewed along oc is shown in
Fig. 4b. The 1D chain extends by intermolecular hydrogen
˚
bonds in ab plane (O8/O4C 2.667(2) A; C KxC1/2, KyK1/
2, KzC1; D: x, Ky, 1/2Cz; E: x, y, zK1; F: Kx, Ky, 1Kz; G:
x, Ky, zK1/2; H: Kx, y, KzK1/2) and generate a 3D
architecture, as shown in Fig. S2.
Fig. 3. ORTEP drawing of 2, drawn with displacement ellipsoids at the 30%
probability.
3.1. Luminescent properties
consolidate the chain framework. Moreover, these zigzag
chains are cross-linked along oc direction by the bifurcated
As shown in Fig. 5, the free H4adip ligand exhibits a broad
strong green-fluorescent emission around 521 nm upon
excitation at 410 nm. Complex 1 exhibits an intense blue
emission at 474 nm upon 380 nm excitation, while complex 2
hydrogen bondsiii of O18/O6D (2.838(5) A; D: KxC1,
˚
˚
KyC2, Kz)) and O18/O15E (2.745(4) A; E: Kx, KyC1,
Kz) to generate 2D layer. Fig. 2b affords the view of the
Fig. 4. (a) 1D zigzag chain extend along oc direction; (b) perspective view down c-axis.

224
Y. Xu et al. / Journal of Molecular Structure 789 (2006) 220–224
Supplementary data
Supplementary data associated with this article can be found,
in the online version, at doi:10.1016/j.molstruc.2005.12.023
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